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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Catecholamines of the adrenal medula and their morphological changes during adaptation to repeated immobilization stress

Changes of the adrenal medulla of rats were studied in the course of adaptation to repeated immobilization stress. An increase in the number of cells in the adrenal medulla was found in the adapted animals; this increase was confirmed by weight indices of the medulla and by cell counts per surface unit. Simultaneous karyometric measurements of the nuclei of adrenal medulla cells and an analysis of the catecholamine contents in the adrenals explain the increased activity of the adrenal medulla in the course of adaptation.

Kvetnansky, R.↗
NASA NTRS1979

Morphology and phenomenology of the high-latitude E and F regions

Results obtained at high latitude observatories on the behavior of E and F region ionization are presented including a bibliography. Behavior of E and F region ionization during day and night for quiet and disturbed conditions in the auroral and polar regions is described. Daily, seasonal and sunspot variations are also outlined.

Hunsucker, R. D.↗
NASA NTRS1980

The relationships between high latitude convection reversals and the energetic particle morphology observed by the Atmosphere Explorer

Simultaneous measurements of the auroral zone particle precipitation and the ion convection velocity by Atmosphere Explorer show a consistent difference between the location of the poleward boundary of the auroral particle precipitation and the ion convection reversal. The difference of about 1.5 degrees of invariant latitude is such that some part of the antisunward convection lies wholly within the auroral particle precipitation region. The nature of the convection reversals within the precipitation region suggests that in this region the convection electric field is generated on closed field lines that connect in the magnetosphere to the low latitude boundary layer.

Heelis, R. A.↗
NASA NTRS1979

Transient brightenings of interconnecting loops - Morphology of the sudden brightenings

Sudden brightenings of coronal loops that interconnect active regions are studied. Such brightenings often occur within one or two days after the birth of a new interconnecting loop, as well as in some old interconnections. The brightenings of young loops are obviously associated with the emergence of new magnetic flux near their footpoints, whereas some enhancements of old loops may be triggered by slowly moving disturbances propagating from other centers of activity. A few loop brightenings are associated with flares, but the loop does not brighten in consequence of the energy supply from the flare. Both the flare and the loop brightening are independent consequences of one common agent, presumably newly emerging flux. Temperatures in brightened loops are between 3 and 4 x 10 to the 6th K and densities are less than 2 x 10 to the 9th/cu cm, probably less than 5 x 10 to the 8th/cu cm in some old loops. The top part of a loop is the site of the most intense brightening in the initial phase of a loop enhancement. The most frequent lifetime of these brightenings is 6 to 7 hr.

Svestka, Z.↗
NASA NTRS1979

Alphonsus-type dark-halo craters - Morphology, morphometry and eruption conditions

The Alphonsus dark-halo craters are sites of volcanic eruptions with a characteristic crater radius of approximately 1 km. They are characterized by dark haloes ranging from 3 to 4 km, by substantial amounts of nonjuvenile material within the deposits, and by a lack of any associated lava flows or prominent constructional features, such as cones or domes. In the present paper, possible eruption styles are analyzed, using these observational constraints. It is concluded that an eruption process analogous to terrestrial volcanian explosive activity provides the most reasonable explanation for the characteristics of the deposits. The dark-halo craters appear to have formed contemporaneously with the emplacement of lavas in the adjacent Mare Nubium.

Head, J. W., III↗
NASA NTRS1980

Morphological changes in neurons of the hind limb reflex arc during long term immobilization

Twelve adult rabbits were immobilized for 9 to 31 days, followed by histological study of the nerve processes of lumbar vertebra 7 and sacral vertebra 1, the sciatic nerve and the motor endings of the thigh muscles. In the spinal ganglia, dystrophic changes of increasing severity with immobilization time were found, including pericellular edema, vacuolized neuroplasm, pycnotic changes, cytolysis and destruction. Chromatophilic matter decreased and was partly bleached, and amitotic division occurred. A portion of the sciatic nerve fibers were argentophilic, and some fragmentary decomposition occurred. Considerable dystrophic changes occurred in the motor nerve endings.

Tkachenko, Z. Y.↗
NASA NTRS1980

Functional-morphological parallels of the hypothalamo-pituitary-adrenal system response reaction to long-term hypokinesia

The effect of 2 and 4 week hypokinesia regimens on the hypothalamo-pituitary-adrenal system (HPAS) was investigated in 110 inbred mice. Progressive exhaustion and pathological reorganization of the HPAS morphofunctional structures was revealed. On the basis of established facts of interlineary and interspecies differences in the HPAS response, it is suggested that the animal body response reaction to the long term effects of hypokinesia depends largely on its HPAS resistance and the values of this system's defensive adaptation potential.

Tsvetov, Y. P.↗
NASA NTRS1980

Martian valleys - Morphology, distribution, age, and origin

The article summarizes the geological and geomorphological evidence concerning the formation of the valley networks of Mars which were observed in the Mariner 9 and Viking Orbiter images. There is no clear evidence of direct fluid erosion in any Martian valley. The networks are diffuse and inefficient, with irregular tributary junction angles and large, undissected intervalley regions. The deeply entrenched canyons, with steep-walled amphitheater terminations suggest headward extension (sapping) by basal undermining and wall collapse. It is believed that valley formation has not occurred on Mars for billions of years because the size-frequency distributions of impact craters in these valleys and in the heavily cratered terrain which surrounds them are statistically insignificant.

Pieri, D. C.↗
NASA NTRS1980

The morphology of metallic ions in the upper atmosphere

Analysis of metallic ion data from a day-night pair of rockets, OGO 6, and the elliptic phases of AE-C and AE-D shows the presence of Fe(+) ions at altitudes above 400 km only at low magnetic latitudes. The detection probability of this ion decreases with altitude, with a maximum over the Atlantic and a minimum over India; the rocket data indicate ions in the E region during the day and on the bottom of the F layer at night. Mg(+) and Fe(+) are the dominant ions below 250 km at all latitudes, but Al(+), Na(+), Si(+), and Ca(+) are also detectable; a correlation was found between solar activity and metallic ion detection probability at low latitudes and high altitudes at night

Kumar, S.↗
NASA NTRS1980

Morphology of the Venus ultraviolet night airglow

Images of the nightside of Venus in the (0,1)delta band of nitric oxide have been obtained by the Pioneer Venus orbiter ultraviolet spectrometer (OUVS). The emission, which is produced by radiative association of N and O, shows a bright spot reaching 5 kR and located at 2 a.m. local solar time just south of the equator. The emitting layer is at 111 + or - 7-km altitude. A one dimensional vertical transport model shows that the hemispheric average brightness of 0.8 kR is consistent with the orbiter neutral mass spectrometer (ONMS) measurements of N and O near 167 km, and that the altitude of the emitting layer is consistent with the eddy mixing model proposed to explain the dayside helium profile measured by the bus neutral mass spectrometer. In the model, N reaches a peak of 7 x 10 to the 8th per cu cm at 114 km, and O reaches a peak of 2.6 x 10 to the 11th per cu cm at 106 km. There is a fair degree of consistency between the ONMS, OUVS, and other airglow measurements, except as regards the local time dependence.

Stewart, A. I. F.↗
NASA NTRS1981

The O II /7320-7330 A/ airglow - A morphological study

A statistical study of the 7320-30 A airglow arising from the metastable transition between aP and aD states of atomic oxygen ions was conducted by analyzing the data taken from the visible airglow experiment on the Atmosphere Explorer satellites C and E during the time periods between 1974 and 1979. Averaged column emission rate profiles as a function of solar zenith angle and solar activity variation are presented. The galactic background has been carefully subtracted. The result shows that the rate of decreasing emission as a function of solar zenith angle agrees with the theoretical calculation based upon a neutral atmosphere model and the solar spectrum as measured by the EUV spectrometer on the Atmosphere Explorer satellite. Furthermore, an expected increase with solar activity also appeared in a plot of emission brightness versus solar 10.7-cm flux.

Yee, J. H.↗
NASA NTRS1981

Morphological study of the time histories of gamma-ray bursts

Time histories of gamma-ray bursts have revealed a great diversity, both in total duration and in the details of fine time structure. Results of the gamma-ray experiment on the Helios-2 spacecraft have suggested some similarities in time profiles of events. The possibility of some characteristic 'separation times' in events may also be indicated.

Desai, U. D.↗
NASA NTRS1981

The generation and morphology of single-crystal silicon carbide wear particles under adhesive conditions

Sliding friction experiments were performed in vacuum at room temperature on a plane-type SiC surface in contact with iron-based binary alloys. Multiangular and spherical wear particles were found to form as a result of multipass sliding. The multiangular particles were produced by primary and secondary cracking of the 0001, 10(-)10, and 11(-)20 plane-type cleavage planes under the Hertzian stress field or local inelastic deformation zone. When alloy surfaces are in contact with silicon carbide under a load of 0.2 N, the alloy around the contact area is subjected to stresses that are close to the elastic limit in the elastic deformation region and/or exceed it. It was also found that spherical wear particles may be produced by two mechanisms: a penny-shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and the attrition and fatigue of wear particles.

Miyoshi, K.↗
NASA NTRS1981

Frictional and morphological characteristics of ion plated soft, metallic films

Ion plated metallic films in contrast to films applied by other deposition techniques offer a lower friction coefficient, longer endurance lives and exhibit a gradual increase in friction coefficient after the film has been worn off. The friction coefficients of metallic films are affected by the degree of adherence, thickness and nucleation and growth characteristics. The effective film thickness for the minimum friction coefficient was established for Au and Pb films. The nucleation and growth characteristics during ion plating lead to a fine, continuous crystalline structure, which contributes to a lower friction coefficient.

Spalvins, T.↗
NASA NTRS1981

Morphology of Saturn's aurora

Aurorally-excited emissions of atomic and molecular hydrogen come from a narrow circumpolar band near 80 deg north and south latitude on Saturn. The aurorae, which lie near the edge of the polar cap region, are continuously excited in both the north and south. If the strong variations observed in the auroral intensity are temporal, rather than longitudinal, they may be related to the periodic structure in the Saturn kilometric radiation.

Sandel, B. R.↗
NASA NTRS1981

The distribution and morphology of X-ray-emitting gas in the core of the Perseus cluster

An unresolved source has been found coincident with the nucleus of NGC 1275 in a high-resolution X-ray image of the core of the Perseus cluster. Absorption in the optical features at high velocity with respect to NGC 1275, which are thought to be associated with a foreground galaxy, does not produce any detectable X-ray absorption. The emission tends to become asymmetric in the presence of the lower-velocity filaments, but no obvious, detailed correlation is found between X-ray enhancements and individual filaments. Deprojection of surface brightness to yield temperature and density profiles of the intracluster gas shows results consistent with a quasi-hydrostatic radiative accretion flow onto NGC 1275, and the pressure-driven mass inflow onto the central galaxy is then 200-400 solar masses/yr. The possibility of a problem in the relation of line-of-sight velocity dispersion to cluster gravitational mass is confirmed.

Fabian, A. C.↗
NASA NTRS1981

A quantitative study of factors influencing lamellar eutectic morphology during solidification

The factors that influence the shape of the solid-liquid interface of a lamellar binary eutectic alloy are evaluated. Alloys of carbon tetrabromide and hexachloroethane which serve as a transparent analogue of lamellar metallic eutectics are used. The observed interface shapes are analyzed by computer-aided methods. The solid-liquid interfacial free energies of each of the individual phases comprising the eutectic system are measured as a function of composition using a 'grain boundary groove' technique. The solid-liquid interfacial free energy of the two phases are evaluated directly from the eutectic interface. The phase diagram for the system, the heat of fusion as a function of composition, and the density as a function of composition are measured. The shape of the eutectic interface is controlled mainly by the solid-liquid and solid-solid interfacial free energy relationships at the interface and by the temperature gradient present, rather than by interlamellar diffusion in the liquid at the interface, over the range of growth rates studied.

Kaukler, W. F. S.↗
NASA NTRS1981

The morphology and evolution of Ganymede and Calisto

Images of Ganymede and Callisto, Jupiter's two largest moons, among the largest known predominantly icy planetary objects, were obtained by the two Voyager spacecraft. Voyager images were used to investigate the surface characteristics, geologic processes, and internal evolution of Ganymede and Callisto. Ganymede shows two principal types of terrain: one dark, old, and heavily cratered; and another brighter, younger, and characterized by complex patterns of grooves. Voyager imagers were used to determine photometric properties of surface features on both bodies at phase angles up to 120 deg. Surface temperatures are calculated for the major terrain types. Callisto is found to be somewhat warmer than Ganymede. The temperature difference between grooved and cratered terrain on Ganymede is small. A model for the origin of grooved terrain is considered in which extension creates broad, downdropped rift zones in the crust that are filled with water or ice from below.

Squyres, S. W.↗